Condenser paper and method of making the same



June 28, 1932. P. SCHWEITZER 1,864,950

CONDENSER PAPER AND METHOD or MAKING THE SAME Filed April 19, 1929 A NEYPatented June 28, 1932 tours r. SOKWEITZEB, or NEW YORK, N. Y. comannsnaram-m AND mmnon or MAKING THE sup:

Application filed April 19, 1929. Serial no. 356,388.

My present invention relates generally to paper manufacture, and hasparticular reference to the manufacture of pa er layers or stripssuitable for use in .Woun condenser bodies.

Before describin the features of my present invention, I will premisethat electrical condensers of the so-called aper dielectric typeconsistessentially 0 a condenser electrical body composed of interwoundlayers or strips of conducting material such as foil and dielectricmaterial such as paper. Because of the nature of such condensers, thequalificationsof the paper entering into their manufacture are accurateand stringent in nature,

and any paper which does not precisel comply with the specificationslaid down y the condenser manufacturer will be rejected by him. Forexample, the paper mustbe of umform thickness throughout its length, itmust be totally devoid of any impurities, particularly those which mightbe electrically conductive, it must embody a certain uniform porosity,etc.

B5 Condenser bodies ofthe foregoin character are usually formed by meansof winding machines. Thus, two rolls of foil ma be suitably mounted inassociation with our I rolls of paper so that six strips may be guid-'l0 ed-toward a mandrel and wound about the latter, each foil strip beingsandwiched. be- 1 tween a pair of paper strips. In a condenser body thusformed, the resultant assembly will have two layers of paper interposedbe- 5 tween each two adjacent foil layers. It frequently' is necessaryor desirable to increase the thickness of the'paper layer interposedbetween the foils, in which case it has been customary to mountadditional paper rolls or more strips of paper are ultimately interposedbetween adjacent foil strips in the wound assembly. It is a generalobject of my present invention to provide a.paper strip which is theequivalent, in the wound condenser body, of two or more strips of thepaper heretofore employed, the single strip or web of the pres-. entinvention thereby serving to simplify r m manufacture of condenserbodies by on the winding machine so that three, four,

avoiding the necessity for extra rolls of paper and the consequentadditional handling and likelihood of wastage thereof.

The important and valuable characteristics of the present inventionwillbe more fully 66 appreciated when I point out that it has beenunsatisfactory in the past merely to manufacture a single-ply paperstrip of increased thickness. It is true that within certain limits acondenser manufacturer may call for different weights of paper. Butwhile he may, for example, specify either a 4-pound or a 5-pound paperstrip (which means that the strip Weighs 4 or 5'lbs. pe'r ream of 480sheets, each sheet 20" x 30") he will not call for nor will he acceptasingle-ply paper of, say, a 12-pound or 15-pound variety but willachieve his purpose by winding two or more of the 4-pound or 5-poundpaper stri s into' the condenser body. The reason for t is lies in thefact that the manufacture of the heavier paper with the prescribed andnecessary degree of accurate uniformity and purity is extremelydifficult, if at all. possible. Uniformity in thickness is moredifiicult to achieve, irregularities in porosity are more likely tooccur, and impurities of a conductive character are harder to avoid, notto speak of the fact that such impurities will be of greater dimensionsbecause of the increased' thickness of the paper. Furthermore, a groupof thin sheets have, together, a greater insulation strength than asingle sheet having the same overall thickness. For example, two. sheetsof .4'mil aper, are better insulators than one sheet 0 a .8 mil paper,etc.

Nor is a multi-ply or so-called duplex? paper of ordinary well-knowncharacter any more satisfactory. Where the manufacture of such multi-plypaper consists in forming two or more webs of paper stock and unit' themprior to the completion of each thereo (particularly so far as dryingis. concerned), the possibility of attaining the requisite uniformitythrough periodic testing and control is .5 absent, for there is no wayof ascertaining, for example, the porosity or weight distribution orpurity of each indlvidual wet web of whlch the duplex paper is made.

In the light of the foregoing, the foetus of my present invention willbe evident when I point out that the single web orstrip of paper which Iproduce is of such a character that its salient characteristics, fromthe standpoint of the condenser manufacturers purposes, are not onlyaccurately uniform, resulting from periodic and even continuous testing,observation, and control, but are of such demonstrable and provableuniformity and character that the paper is acceptable by ployed bycondenser manufacturers.

It is a feature of my invention to provide a paper which is from oneaspect a composite paper, being formed of individual strips of papereach by itself accurately uniform in weight, porosity, and other vitalcharacteristics, and each by itself being, as a matter of fact, of thevery character heretofore employed by condenser manufacturers.

One feature of my invention lies in providing this desirable type ofpaper strip without any recourse to adhesive, sizing, or to the use ofsimilar foreign substances to which the condenser manufacturer wouldproperly object.

A further feature of my invention lies in providing such a paper withoutthe necessity for re-designing or re-modeling the wellknown Fourdriniermachines upon which the condenser paper of the present day iscustomarily made. As a matter of fact, my present method of manufactureinvolves the completion of the individual component paper strips uponthe Fourdrinier machine or machines in the same manner as heretofore,and resorts to subsequent treatment of the paper strips to achieve thedesired end.

Briefly, I provide my present improved type of condenser paper bycompressively uniting two or more individual strips each of which iscomplete in itself except that it remains uncalendered.

In the accompanying drawing I have diagrammatically illustrated mypresent invention.

Figure 1 illustrates a method of treatment of individual paper stripswhereby my invention may be carried into effect;

Figure 2 is a perspective view of a condenser body of the character forwhich my improved paper is designed; and

Figure 3 is a view similar to Figure 1, illustrating a modification.

In accordance with my present invention I first produce two or morepaper webs or strips upon a Fourdrinier machine or machines in tnewell-known manner, each of these strips being,'for example, a .4 mil or.5 mil condenser paper of the character heretofore widely used bycondenser manufacturers. Although not illustrated in the drawing, I willstate briefly that each strip is manufactured by forming and advancing aweb of paper stock, such stock being composed of nothing more than paperpulp and pure se4,eso

water. During the advancement of the web it is successively passed overa number of felts of well-known character, between various press rolls,and ultimately over a set of dryer rolls which are suitably heated.Until the web is self-sustaining it is impossible to accuratelyascertain its qualities for the purpose of controlling the same. Duringthe completion of each web, however, it is not only possible butnecessary and customary to test successive samples at periodicintervals, and in some cases continuously, to ascertain the weight andother characteristics and adjust or control the manufacture accordingly.For example, at least twenty-four times a day a sample of the paper issubjected to a test whereby the presence of electrically conductiveimpurities may be detected; on even more occasions the porosity istested by a suitable meter and one or more of the in; numerable factorsaffecting the porosity are thereupon adjusted or controlled. In asimilar manner, the weight of the paper may be either continuously orperiodically measured to furnish a similar basis for continuous controlof weight-uniformity.

In Figure 1 I have shown three rolls 10, 11, and 12 of condenser papermanufactured in the foregoing manner. This paper would be ordinarilyacceptable without question by the condenser manufacturer except thateach roll wouldusually be subjected to a calendcring process which Iomit. The paper strips 10, 11', and 12' leading from theserolls areguided into superposed relationship between a pair of rollers 13 and 14,the former being preferably of rubber or the like, and the latter beingof brass or similar non-rusting material. The rolls 13 and 14 are somounted as to be adjustable in compressive relationship whereby theplies or strips passing therebetween will be squeezed together.

Suitable means are provided for rewetting the paper strips during thecompression thereof and I have illustratively shown a container 15within which a supply of pure or distilled water 16 is contained, theroller 13 being so mounted as to be immersed at least in part within thewater 16. i

' The roller 13 is driven and drives the roller 14 by frictionalengagement therewith. The roller 13 picks up water from the container 15and serves to wet the plies passing between the two rollers.

The successful carrying out of my present invention lies in the fact,which I have ascertained by actual ex eriment, that completely dried butuncalen cred paper strl s of the character shown and described mayactually united into a single mass under the combined action ofcompression and rewetting. The composition of each individual strip isunaffected by this treatment since nothing but pure water was originallyemployed as a carrying medium for the pulp. It is most probable that therewetting softens the fibers of pulp and facilitates the intimateinter-i locking of the exposed fibers on the surfaces of the strips. Reardless of the particular action which is e ected, I have found thatrequisite uniform qualities, composition and characteristics to renderit acceptable by condenser manufacturers for use in the winding ofcondenser bodies, has, I-believe, been unknown up to the present time;

The strip 17 is caused to pass around several dryer'rolls 18 and 19 ofthe character employed on the well-known Fourdrinier machine, and it isfinall subjected to a calendering process (not in icated on the drawing)which renders it ready for use in the winding of condenser bodies.

, In Figure3I have shown a slightly modified arrangement wherein thestrips 11', and

' 12 are passed beneath the roller 13, thereby facture of paper becomingcompletely immersed within the water in the container 15. In thisinstance, the plies pass between the rollers in the opposite directionbut are thereafter conducted as a single resultant web 17 aroundthedryer rolls 18 and 19, and are ultimatel subjected to the calenderinabove referred to.

In Figure 2, I have illustrated the type of condenser body with which mypresent pa r is to be used. I have shown a air of il strips 20 and 21,each thereof ing sandwiched between aair of paperstrips. The foil strip21 is sand wiched between the strips 22 and 23, and the foil strip 20 issandwiched between the paper strips 24 and 25. The winding machine uponwhich this body v.is made will be provided with six spindles upon whichthe corresponding rolls of paper and foil willbe mounted Withoutalterlngf'this winding machine and thereby complicating the manufacture,my paper makes it possible to provide condensers of diiferingcharacters. For example, if each of the strips 2225 is of a singlefour-pound type of paper, then a condenser of a particular'capacity willbe produced. Vhere additional paper rolls have heretofore been added forthe production of condensers of greater capacity, it is now onlynecessary to employ paper strips of the character shown at' 17. A-condenser thus resulting will have a capacity equal to that which wouldhave heretofore required the addition of eight spindles to the windingmachine; y

It will thus be seen that I have provided a novel type of paper for usein the manuielectric condensers, the

homogeneous web, and finally v sustaining,

uniformity of weight, porosity, and purity being such as to render thepaper acceptable by condenser manufacturers. The accurate control duringthe manufacture of the individual strips of which my present paper stripis made assures a proper quality; the absence of any sizin or othersubstance foreign to the indivi ual strips by, themselves obviates anyobjection on this score;

and the employment of asin le strip in place of a plurahty of separatedindividual strips in the winding of condenser-bodies is a highlydesirableadvantage which my inventlon renders pomible. I

It will be obvious that changes in the details herein described andillustrated for-the purpose of explaining the nature of my invention maybe made by those skilled in the art without departing from the spiritand scope of the invention as'expressed in the appended claims. It istherefore intended that these details be interpreted as illustrative,and not in a limitin sense.

Having thus describe my invention and illustrated its use, what I claimas new and desire to secure b Letters Patent is-- 1. The herein-.escribed method of making a paper insulatin layer for an electricalcondenser body, w ch consists in compressively' associating atcalendered webs of uncoated paper into s'uleast two dry and 1111-.

perposed relationship, wetting said webs withwater during saidassociation whereby they will physicall unite to form a single web ofincreased t ickness, and finall expelling said water, whereby the resutant web is substantially homogeneous throughout.

2. The herein-described method of makin a.,paper insulatin layer for anelectrica condenser body, w ich consists in guidin a plurality ofuncalendered and uncoated ut otherwise complete paper webs intosuperposed relationship between a pair of pres sure rollers, immersingone of said rollers at least partially into a supply of distilled wa-.ter, whereby said webs will be wetted during their p through saidroller pair, the

fibers of theadjacent surfaces thereby unit in physically with eachother to bond the fb together into a single, substantially drying andcalenderingthe resultant sing e web.

3. The herein-described method of making a paper insulatin layer for anelectrical condenser body, which consists in continuously forming andadvancin a.- web of paper stock composed of pulp and water, treatingsaid web to dry the same and render it selfwhereby the weight, porosity,and purl thereof may be -periodically ascertain and controlled; forming,ad,- vancing and-treating a second web in the same manner; thereuponsqueezing said webs under pressure into superposed association,

rewetting the same with water during said association, so that thefibers of the ad1acent surfaces of said webs will physically unite toform a substantially homo nous web of increased thickness, and thenrying said resultant web to expel said water.

4. As a new'article of manufacture, a paper insulating la er for use ina wound electrical condenser ody, said layer comprising a plurality ofcompressively united superposed individual paper strips each of which isuniform throughoutits length in weight, porosity, and purity, and thefibers of the adjacent surfaces of said strips being physically andnon-adhesively intertwined.

5. The herein-described method of making a paper insulating layer for anelectrical condenser body, whlch consists in squeezing a plurality ofdry and uncalendered paper webs composed of pulp fibers into superposedrelationship, each web being of uniform porosity and thicknessthroughout, wetting said webs with a non-adhesive liquid durin thesqueezing thereof to cause the fibers o the adjacent surfaces of saidwebs to intertwine with each other and form a single, substantiallyhomogeneous web of increased thickness, and finally drying andcalendering said resultant web to expel said liquid.

In witness whereof I have signed this specification this 17 day ofApril, 1929.

LOUIS P. soHwEITzER.

